This invention relates to internal combustion engines and more particularly to a mechanism for converting reciprocating movement of a piston to rotating output movement.
Conventional internal combustion engines include at least one cylinder within which a piston reciprocates. The piston is connected to an output crank by an elongated connecting rod pivoted at an upper end to the piston and at a lower end to the crank. An air/fuel mixture is taken into the cylinder, compressed by the piston and ignited by a spark ignition system. As the ignited air/fuel mixture expands, the piston is forced downwardly during the power stroke of the engine. The piston, through the connecting rod, imparts torque to the crank of the crankshaft, causing the crankshaft to rotate.
During the power stroke of a typical engine, the peak pressures within the cylinder are not experienced when the effective moment arm between the piston and the crank is at a maximum. This reduces the efficiency and power output of the engine and is the result of the kinematics inherent in the piston, rod and crank structure. Various proposals have been made to delay the attainment of peak pressures until the piston moves beyond top dead center and the mechanical advantage or torque output is maximized. Such proposals have included apparatus to provide a delayed pressure increase to compensate for combustion chamber volume increase during the power stroke. These approaches are discussed in my earlier application Ser. No. 950,368, filed Oct. 11, 1978, and now U.S. Pat. No. 4,211,082.
During the operation of conventional internal combustion engines, significant losses or reduction in mechanical advantages occur due to the angular relationships of the piston, connecting rod and conventional crank arm. At top dead center, no torque can be transmitted through the crank. Increased torque and hence a decrease in loss occur as the engine goes through the power stroke. The useful work obtained is a function of an ever-changing amount of pressure within the engine combustion chamber multiplied by the infinitely small distance the piston, rod and crank have moved at each pressure. This is according to the principle of resultant forces which is at work in the process. At the same time, the compound angular application of the pressure causes additional friction on the cylinder walls resulting in additional losses in efficiency. Because these losses are substantial, a need exists for a mechanism which will lessen the angle at which the pressure is applied and increase the distance which the lower end of the connecting rod moves under more favorable torque conditions.
Various attempts have been made to eliminate the conventional connecting rod and crank mechanism to increase the mechanical efficiency or torque output and to reduce other losses caused by the nonlinear movement of the connecting rod during the power stroke. An example of one such proposal may be found in U.S. Pat. No. 1,505,856, entitled EXPLOSIVE MOTOR and issued on Aug. 19, 1924 to Briggs. This patent discloses an internal combustion engine including a piston reciprocating within a cylinder. A crank is offset from the vertical centerline of the piston and is connected to the piston by a vertically moving rod and cam block. The block defines an elongated cam slot within which a crank pin is slidably disposed. The rod is guided for linear, vertical up and down movement. The piston, during the power stroke, applies force to the crank along a line which approaches a perpendicular. Also, offsetting of the cylinder with respect to the crank reduces the side thrust or loading and hence frictional losses.
Other engines wherein a connecting rod moves along in an essentially vertical line and wherein a conventional crank is eliminated may be found in U.S. Pat. No. 1,667,213, entitled INTERNAL COMBUSTION ENGINE and issued on Apr. 24, 1924, to Marchetti; U.S. Pat. No. 2,407,859, entitled MECHANICAL MOVEMENT and issued on Sept. 17, 1946, to Wilson; U.S. Pat. No. 2,757,547, entitled UNIVERSAL DOUBLE TORQUE ENGINE and issued on Aug. 7, 1956, to Julin; and U.S. Pat. No. 3,916,866, entitled ENGINE HAVING RECIPROCATING PISTON AND ROTARY PISTON and issued on Nov. 4, 1975, to Rossi.